Messenger uses a 'signature' when it connects. You can use 'user agents' to block MSN and many other things of this nature.
Right-click your outgoing allow rule(s) and select configure http. Select the signatures tab and add as needed.

rsivanandan - Thanks for the link, but im sorry to say it doesn't work. :-(

Make your Skpe connections; what are the ports that are being used for each function?

Well that is a part of the problem - Skype is very agressive and uses randomly ports to connect through, from port 0 ---> 65535 to connect. So blocking it makes it almost impossible.

Bu the intesting is blocking file transfers - Skype uses AES 256-bit encryption - so its a secure line when using it for business communicartion. So we dont wont to block that part. Only transfers for security reasons so employees cannot send/recieve files.

This is a trial and error. There has to be a difference in the signatures or the data traffic or the make-up of the packets otherwise the receiving end would not know the difference between voice/data flows. Still looking. What have you found out from your end?

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